The present invention relates to a conductive sheet, particularly, to a conductive sheet having a conductive portion in which a volume ratio of metal silver to gelatin is within a predetermined range.
Furthermore, the present invention relates to a manufacturing method of the conductive sheet and a touch panel including the conductive sheet.
A conductive sheet, in which thin conductive wires have been formed on a support, is widely used in a transparent electrode of various electronic devices such as a solar cell, an inorganic EL element, and an organic EL element, an electromagnetic wave shield of various display apparatuses, a touch panel, a transparent sheet-type heating element, and the like. Particularly, in recent years, as a touch panel has been more frequently mounted on cellular phones or mobile game consoles, a demand for a conductive sheet for capacitance type touch panels that can perform multipoint detection has rapidly increased.
As a method for forming such a conductive sheet, a method for forming thin conductive wires with low resistance from a silver image, which is obtained by developing a silver halide photographic sensitive material, is under examination. For example, JP 4895536 B suggests, as a method for obtaining a transparent conductive material having high transparency and conductivity with excellent productivity, a method of decomposing gelatin by treating the gelatin with an enzyme-containing treatment solution which contains an enzyme acting on gelatin.
The silver-containing thin conductive wires manufactured from the silver halide photographic sensitive material have a problem in that ion migration easily occurs. When the ion migration occurs between the thin conductive wires, the thin conductive wires become conductive to each other, and thus the wires cannot function as a circuit.
Particularly, in recent years, as the products have been required to be further miniaturized and to demonstrate higher performance, the wiring interval has been further narrowed, and therefore the conduction of a circuit has more easily occurred due to ion migration. For example, in the field of touch panels, a busbar and lead-out wirings are desired to be formed such that they are positioned within a very narrow frame range at the edge of a panel. Consequentially, in this situation, the space between wirings in a peripheral wiring portion is reduced, and thus conduction easily occurs due to ion migration.
In contrast, when the wiring interval is narrowed as described above, the conductive sheet manufactured by the method described in JP 4895536 B does not always exhibit a sufficient effect with respect to ion migration, and thus, the ion migration inhibition effect of the conductive sheet needs to be further improved.